Bayesian monitoring of a phase 2 chemoprevention trial in high-risk cohorts for prostate cancer

The objective of phase 2 cancer chemoprevention trials is to evaluate wheth er a chemopreventive agent will cause significant modulation of intermediat e endpoint biomarkers (IEB) in patients at high risk for the disease. A pha se 2 chemoprevention trial of 4-hydroxyphenyl retinamide (4-HPR) Versus pla cebo was conducted in men with a histologic diagnosis of early prostate can cer and scheduled to have radical prostatectomy. A Bayesian monitoring meth od was used to sequentially monitor this trial for evidence of biological a ctivity or ineffectiveness based on a single IEB variable. Different prior distributions were used and posterior distributions were obtained to calcul ate the probability that treatment differences are greater than or less tha n a predetermined clinically significant effect. The interim analysis of tr ansforming growth factor-st expression indicated a high probability of insu fficient biological activity of 4-HPR on this IEB, This study demonstrates the potential utility of Bayesian methods in the decision-making process in the conduct of phase 2 chemoprevention trials.